Approach:
Sows must remain in the breeding herd for 3 to 4 parities to produce enough weaned piglets to be profitable. This plan describes experiments that focus on gilt development, the number of piglets weaned, and retention of sows in the breeding herd. These three factors have been identified by the National Pork Board as high priority research topics, because they each affect sow lifetime productivity. Genomic approaches will be used to develop genetic markers to improve these traits, taking advantage of animal numbers and critical expertise in genomics at USMARC. In addition, experiments focused on gilt development will elucidate factors contributing to the effects of litter birth environment of gilts before weaning on puberty, bone development and retention of sows in the herd. Factors contributing to litter size such as genetic imprinting, control of fetal blood flow, and arginine supplementation during pregnancy will be investigated. Factors contributing to preweaning survival such as development of energy stores within the fetus and neonate, the role of lactation and neonatal activity, and the effect of timing of farrowing induction will be investigated. Experiments focused on retention of sows in the breeding herd will investigate metabolic activity of the sow, with special attention to the demands and consequences of lactation on sow postweaning return to estrus. These experiments are enhanced by the expertise in these areas of the personnel assigned to the project. We expect to provide the swine industry with information, management strategies and genetic markers that will improve sow lifetime productivity.